Multiple Race Inoculation as an Option in Breeding for Resistance to C. Lindemuthianum In Common Beans

Bean anthracnose caused by Colletotrichum lindemuthianum causes severe common bean (Phaseolus vulgaris L.) yield losses of up to 100% worldwide. Breeding for resistance is the best method to mitigate this problem. The objective of this study was to investigate the appropriateness of C. lindemuthianum multiple race inoculation in breeding for resistance to C. lindemuthianum in common bean. Seven parents with varying reactions to Colletotrichum lindemuthianum were mated in all possible combinations to generate fourty-two progeny crosses. These crosses together with their parents were evaluated in the green house for their reaction to C. lindemuthianum. The experiment was laid out following a Completely Randomised Design (CRD) with four replications. The treatments used were: (1) inoculation with race 54; (2) inoculation with race 311 and (3) multiple inoculation of race 54 X race 311. The mean genotypic score among treatments were found to be 1.76, 2.62 and 3.06 for treatments 1, 2 and 3 respectively. There were significant differences (P < 0.01) among genotypic responses to C. lindemuthianum with respect to race 311. The t-test analysis revealed that multiple race inoculation (Treatment 3) had a higher mean disease severity expression than those of singly race inoculations (Treatment 1 and Treatment 2) (P< 0.01). The results suggest that multiple infection had a synergistic effect, indicating its suitability for screening resistant genotypes in the breeding program.